The subject matter disclosed herein relates in general to the initiation of devices located on a spacecraft, and in particular to a system which controls the initiation of non-energetic hold-then-separate devices located on a spacecraft.
Launch vehicles typically have multiple stages and are used to carry payloads during travel away from the Earth's surface after the vehicles are launched, and then place or deploy the payloads into orbit or beyond. These payloads are commonly referred to as satellites if they are intended to orbit a body (e.g., Earth) after deployment, or as spacecraft if they are intended to leave the Earth's orbit after deployment. Sometimes the terms “satellites” and “spacecraft” are used interchangeably.
Spacecraft typically utilize hold-down and release mechanisms (“HDRMs”) (i.e., a “hold-then-separate” device) to securely hold, retain or stow elements of the spacecraft during launch. These elements, such as solar arrays, antenna reflectors, radiators, instrument booms, propulsion pointing actuators, doors, sensors, etc., are deployed as desired by activating the hold-down and release mechanisms.
An HDRM is generally an electro-mechanical, “one-shot” device in that after it is activated to release its stowed or held element, the HDRM either needs to be replaced, refurbished, or reset—depending on the type of technology that the HDRM employs. An HDRM is typically not a motorized device or other type of device that will return to its original state without some type of external intervention.
HDRMs are generally broadly categorized into three different types: explosive, pyrotechnic, and non-explosive—depending upon the type of activation or actuation mechanism utilized. Explosive and pyrotechnic HDRMs are also both typically referred to as energetic HDRMs, while a non-explosive HDRM or a non-pyrotechnic HDRM is also typically referred to as a non-energetic HDRM. An explosive HDRM is one whose activation mechanism detonates on command, while a pyrotechnic HDRM is one whose activation mechanism burns or deflagrates on command. A non-energetic HDRM is one that typically utilizes an activation mechanism such as a fuse wire or link wire that heats and weakens on command from a control unit when an amount of electrical current passes through the wire, thereby causing it to melt and break. Other types of non-energetic HDRMs utilize a shape memory alloy or utilize the volumetric expansion of certain materials, such as paraffin, when changing from solid to liquid phase. For simplicity, the discussion herein will focus on the fuse wire or link wire style but it can be seen that embodiments of the present invention described herein would be applicable to all types of non-energetic HDRMs.
In a particular type of non-energetic HDRM, when the fuse wire breaks, a release wire that was wrapped around and thereby enclosing the two parts or halves of a cylindrical split spool assembly is released, thereby releasing for movement a pre-loaded device (e.g., a bolt) attached to the split spool assembly. Release of the bolt subsequently releases a stowed element of the spacecraft. This type of non-energetic HDRM is commonly referred to as a split spool release device (“SSRD”). Other common types of non-energetic HDRMs are commercially available.
In the relevant art, it is known that the relatively broad combination of a control unit, a plurality of energetic devices, and an interface bus through which signals (e.g., power and data) are sent and received as between the control unit or controller and the energetic devices (i.e., two-way communication) is generally referred to as a “networked initiation system.” It is a distributed type architecture in which the various components (e.g., the control unit and the energetic devices) are located at different places on the vehicle and are all connected by the interface bus.
Networked initiation systems are known that are used strictly with various types of energetic devices. What is needed is a networked initiation system for use solely with non-energetic HDRMs. What is also needed is a networked initiation system for use with both non-energetic HDRMs, energetic HDRMs (i.e., a “mixed” network initiation system), and/or other (generic) energetic devices (such as a pyro valve or other energetic device used on a spacecraft).